The present invention relates to a vital information processing apparatus capable of effectively reducing noise components contained in vital information and, more particularly, to a vital information processing apparatus which can extract each vital signal representing an electrocardiogram, blood pressure, pulse wave, respiration, EEG (electroencephalogram), or the like and has, as a processing target, Korotkoff sounds, blood pressure, electrocardiogram, respiration, an image data signal representing MRI, CT, radioisotope, or the like.
In a vital information processing apparatus for detecting and processing a vital signal, a vital signal to be detected is generally a signal having a very low level and contains a large number of noise components. For this reason, demand has conventionally arisen for effectively reducing the noise components contained in the vital signal prior to processing of vital information.
To reduce the noise components, the following conventional methods are used. The reference waveform of a vital signal is compared with the waveform of a detected signal to extract only signals having high similarity degrees. Alternatively, the feature points of a signal are extracted to detect the generation period of the signal in accordance with the generation period of the feature points, and signal components falling outside the generation period of the signal are eliminated.
In the method of extracting signals having high similarity degrees, all the signals to be processed must be precisely compared with the reference waveform. That is, to make an accurate judgment, a very large volume of information must be processed. This method cannot be used when vital signals are processed in real time. When vital signals are to be forcibly processed in real time, the processing speed of an apparatus must be increased. The apparatus becomes inevitably bulky and expensive as a whole.
In the method of detecting the generation period of the signal and eliminating signals falling outside this generation period, a filter for passing only signals in a signal band using the signal periodicity is arranged, and a signal having a desired frequency is defined as an effective signal using this filter. According to this method, however, a noise signal whose frequency is greatly shifted from the frequency band can be reduced, but a noise component present in the same frequency band as that of the effective signal cannot be reduced.